JPH03214581A - Spark plug with electric heater - Google Patents

Abstract

PURPOSE:To manufacture spark plug with heater uncostly and with less labor by applying electroconductive paste to the whole peripheral surface of the leg of an unbaked insulating body when the insulating body remains out of baking. CONSTITUTION:Stays 810, 820 are inserted through a shaft hole 210 of an unbaked insulating body 200 and set on a rotary jig 800. This rotary jig 800 is fitted with rollers 830, 840, 850, 860, and three unbaked heat emitting wires 310 are pad printed by rotating the unbaked insulating body 200 and changing the pad position. Each unbaked heater electrifying electrode is pad printed by the use of electroconductive paste having a low electric resistance value after baking process. Thereby reduction of the manufacturing cost is achieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a spark plug with an electric heater arranged in the long leg portion of an insulator in order to prevent contamination and to improve low-temperature startability of an internal combustion engine using hard-to-ignite fuel. ．． However, as shown in FIG. 9 of the prior art, Japanese Utility Model Application No. 55-10239 discloses that a ceramic heater 1 is attached to the long leg portion 101 of the insulator 100.
A spark plug C with an electric heater is disclosed, which is formed by integrally combining the spark plugs 10 and 10.

[Problems to be Solved by the Invention] However, the conventional spark plug C has drawbacks such as the resistance heating pattern layer being deformed or soaked when wound around a raw insulator, causing a change in resistance value. ．． Therefore, the present inventors have developed a spark plug with an electric heater that solves the above-mentioned drawbacks by applying a conductive paste to the surface of the unfired long leg portion of the insulator when it is unfired. The application has been filed under No.

However, according to this technology, it is necessary to create areas where the conductive paste will not adhere, and it is also necessary to form electrodes for energizing the heater at both ends of the paste, which is time-consuming and reduces manufacturing costs. A new problem has been discovered that increases the price. An object of the present invention is to provide a spark plug with an electric heater that can be manufactured easily and at low cost.

[Means for Solving the Problem] In order to achieve the above object, the present invention includes a cylindrical metal shell;
an insulator with a shaft hole that is fitted into the cylindrical metal shell; a ceramic heater whose electric heating path is covered with a ceramic insulating layer and which is integrally coupled to the long leg portion of the insulator; and the electric heating path. a pair of heater energizing electrodes taken out from the
In the spark plug with an electric heater, which is provided with a center electrode inserted into the shaft hole, when the insulator is unfired, a conductive paste is applied over the entire circumference of the surface of the long leg portion of the unfired insulator. We adopted a configuration in which an electrical heating path was formed and the electrodes for energizing each heater were placed approximately opposite each other. [Action and effects of the invention] A. Since the conductive paste is applied to the entire circumference of the long leg surface of the unfired insulator when the insulator is unfired, the electrical heating path can be easily formed without taking much time to apply the paste. Therefore,
Manufacturing costs can be reduced.

stomach. Since the electrodes for energizing each heater are taken out almost oppositely, the electric heat generation paths around both sides have approximately the same electrical resistance value, and the heat generation is not biased. [Example] A first example of the present invention will be described based on FIG.

As shown in FIG. 1, a spark plug A with an electric heater has an insulator 2 with a shaft hole 21 fitted into a cylindrical metal shell 1. As shown in FIG. A ceramic heater 5 formed by covering an electric heating wire 3 with a ceramic insulating layer 4 is integrally connected to the long leg portion 22 of the insulator 2. A pair of heater energizing electrodes 6 and 7 are taken out from the electric heating wire 3. Further, the center electrode 8 is inserted into the shaft hole 21 and fixed thereto.

The cylindrical metal shell 1 has an outer electrode 11 welded to its tip surface, and a screw 12 formed on the outer periphery of the tip.

The insulator 2 is formed of a ceramic sintered body mainly made of alumina, and the length of the long leg portion 22 is 11.0 mm, and the outer circumference is 6 mm.
The length of the small diameter portion 24 is 5 mm, the distance between the tip of the small diameter portion 24 and the front end surface of the insulator 2 is 3 mm, and the wall thickness of the small diameter portion 24 is 1.65 mm.

The number of electric heating wires 3 in this embodiment is three, and they are provided around the small diameter portion 24 of the insulator 2.

The ceramic insulating layer 4 is a fired body of alumina paste, and is formed so as to fill the small diameter portion 24. The heater energizing electrodes 6 and 7 are taken out from the electric heating wire 3, facing each other at 180 degrees. Electrode 6 is insulated 2
Half of the circumference is exposed at the base of the metal shell 1, and electrical continuity is established with the metal shell 1 via the packing 13. The center electrode 8 is made of a nickel alloy, and has a diameter of 1.9 mm at the tip and a diameter of 2.0 mm at the rear end. Next, the manufacturing method of spark plug A with electric heater (
The main parts) will be described along with Figures 2 to 4. (1) 70% by weight of tungsten powder and 30% by weight of alumina powder are mixed, and a binder is added to produce conductive paste 300.

(2) As shown in FIG. 2, the paste 300 is applied with an ink brush 920 onto a concave plate 910 in which a concave portion 911 of 60 μm is formed.

(3) Excess paste 301 is removed using a doctor blade 930 so that the recess 911 is filled with the paste 300. (4) A hemispherical pad 940 made of silicone rubber is pressed against the recess 911, and the paste 300 is attached to the pad 940.

(5) As shown in FIG. 3, the support rods 810 and 820 are inserted into the shaft hole 210 of the green insulator 200 and set in the rotating jig 800. Rollers 830, 840, 850, and 860 are attached to this rotating jig 800. Rotating the green insulator 200 manually or automatically,
By changing the position of the pad 940, three unfired heating lines 310 are pad printed.

(7) Using a conductive paste that has a low electrical resistance value after firing, each unfired heater energizing electrode is printed with a pad. (8) Fill the recess 220 of the unfired insulator 200 with alumina paste (not shown) and fire simultaneously. (9) Shaft hole 2
The center electrode 8 is inserted into the cylindrical metal shell 1 and fixed, and the insulator 2 is fitted into the cylindrical metal shell 1 to form a spark plug A with an electric heater.

The spark plug A with an electric heater of this embodiment has the following effects.

Ah, during the manufacturing process shown in FIG. 4, there is no need to create areas where the conductive paste 300 is not applied, so there is no need to precisely rotate the green insulator 200. Therefore, a simple configuration for controlling the rotation of the rotary jig 800 is sufficient. stomach. Since the electric scrapers 6 and 7 for energizing the heater are separated, there is no risk of short circuit, and positioning during pad printing is easy. Note that the exposed part of the heater energizing electrode does not need to be exactly half the circumference. cormorant. The area that does not generate heat is reduced, and the electric heating wire around
It also heats up evenly. picture. When the electric heating element I13 is made of the same material, the same thickness, and the same number of parts as in Japanese Patent Application No. 1-98493, the amount of heat generated will be about twice as much. Next, a second embodiment of the present invention will be explained based on FIGS. 6 to 8. The method for manufacturing the ceramic heater portion is as follows.

1. As shown in Fig. 6, the unfired exothermic wire 310 is directly printed on the unfired insulator long leg portion 230 (there is no recess) by pad printing similar to Example 1. 2. Figs. As shown in FIG.
Similarly, by pad printing, printing is performed directly on the surface of the unfired insulator 200 facing 180 degrees.

3. After printing, perform the first firing. 4. Alumina powder is thermally sprayed to remove the exposed portion 601, unfired heating wire 310, and unfired heater energizing electrode 60.
Coat 0.700.

5.Furthermore, perform the second firing. In this embodiment, since no recesses are formed in the green insulator 200, the step of forming the recesses can be omitted. In addition to the above embodiments, the present invention includes the following embodiments. a. The heater energizing electrode 6 is exposed at the base of the insulator 2 for half a circumference in order to make good electrical connection with the packing 13, but it may be more than half the circumference, or it may be configured so that only the width of the electrode 6 is exposed. ．． b. The shape, width, number, thickness, electrical resistance value, and conductive material of the electric heating wire 3 may be determined as appropriate.

[Brief explanation of drawings]

Fig. 1 is a half sectional view of a spark plug with an electric heater showing the first embodiment of the present invention, Fig. 2 is a conceptual illustration of pad printing, and Figs. 3 to 5 show pad printing on the spark plug. These are a cross-sectional view, a top view, and a right side view of the rotating jig used for this purpose. FIG. 6 is an explanatory diagram showing a state in which an unfired heating wire is formed on an unfired insulator according to a second embodiment of the present invention, and FIGS. 7 and 8 are an explanatory diagram showing a state in which an unfired heater energizing electrode is printed. It is an explanatory view showing this. FIG. 9 is a sectional view of a conventional spark plug with an electric heater.

Claims (1)

[Scope of Claims] 1) A cylindrical metal shell, an insulator with a shaft hole fitted into the cylindrical metal shell, and an electric heating path covered with a ceramic insulating layer, and a long leg portion of the insulator. A spark plug with an electric heater comprising: a ceramic heater integrally coupled to the insulator; a pair of heater energizing electrodes taken out from the electric heating path; and a center electrode inserted into the shaft hole; The electric heating path is formed by applying a conductive paste to the entire circumference of the long leg surface of the unfired insulator when the heater is unfired, and the electrodes for energizing the heaters are provided substantially opposite to each other. Spark plug with electric heater.